1. Field
The present disclosure relates to a one time programmable non-volatile memory, hereinafter, referred to as “OTP-NVM,” semiconductor device. Such an OTP-NVM is a type of an electrically programmable read only memory, hereinafter, referred to as “EPROM.” The present disclosure also relates to a semiconductor device with improved credibility and storage reliability through increasing generation of hot carrier injection, hereinafter, referred to as “HCl.”
2. Description of Related Art
An EPROM which is used as an OTP-NVM cell is able to electrically store or remove data. Further, such an EPROM is advantageous in storing data without power. Thereby, recently such an EPROM is widely used as an embedded component in various logic devices. For example, an EPROM is a core device composing a micro controller unit, hereinafter, referred to as a “MCU.” In such an example, the MCU controls all electric or electronic products such as home appliance, remote controller, or color TV, in a manner which is similar to the operation of a CPU controlling a computer.
When the hot carriers HC are generated near the drain region of a PMOS in the OTP-NVM cell, hot carriers are injected by hot carrier injection HCl into the OTP floating gate. When electrons are charged in the OTP floating gate, the OTP-NVM cell is read as “1” and when the electrons are discharged the OTP-NVM cell is read as “0.” The more HC is effectively injected, the more the rapid electric field change that is generated near the drain region. In such an example, the state in which the electrons are charged is referred to as programming “PGM.”
When using a logic device which is fabricated through a logic process, HC is less injected in such a process because a lightly doped drain, hereinafter, referred to as “LDD” region is formed in the drain region. This approach of having HC be less injected occurs because, due to the presence of the LDD region, a rapid electric field change is not formed in the drain region, but instead a mild electric field is formed.
When HC is lightly injected into the floating gate during the programming state, that is, when the amount of electrons injected into the floating gate is small, the read current decreases during a reading operation. Accordingly, there is a problem that the OTP-NVM cell is read as not programmed since the read current is detected as smaller than a reference current, and even though there is supposed to be programming, it is not detected.